Smoke suppressant compositions for petroleum fuels

ABSTRACT

The invention disclosed herein is a liquid fuel composition having reduced soot and smoking characterized comprising a major proportion of a liquid hydrocarbon fuel and a minor proportion of Group IIA and Group IIB metal salts of carboxylic acids. A preferred fuel composition is from 0.1 to 0.6 percent by weight of barium- and zinc 2-ethylhexanoates admixed in diesel fuel, wherein the weight ratio of barium to zinc is about 10 to 1. Further improvement in smoke and soot reduction is obtained in hydrocarbon fuels when an ether is additionally incorporated into the salt and fuel mixture. A mixture of from about 0.1 to 0.6 percent by weight of barium 2-ethylhexanoate and zinc 2ethylhexanoate, from between 0.2 to 0.5 percent by weight of the monomethyl ether of ethylene glycol and the balance, a diesel fuel, has substantially reduced smoke and soot forming characteristics.

United States Patent Badin 1 Feb. 1,1972

[72] Inventor:

[73] Assignee:

Elmer .1. Badin, l-lightstown, NJ.

Cities Service Oil Company, Bartlesville, Okla.

221' Filed: Jan. 2, 1968 211 Appl.No.: 694,819

[52] 11.8. C1 ..44/66, 44/68, 44/70, 44/77 [51] 1nt.Cl ..C101 1/18,C101 1/30 [58] Field of Search ..44/57, 66, 68, 70, 77

[56] References Cited UNITED STATES PATENTS 2,221,839 11/1940 Lipkin ..44/57 X 2,560,542 7/1951 Bartleson et a1. .....44/68 X 2,763,537 9/1956 Barusch et a1. .....44/77 X 3,348,932 10/1967 Kukin ..44/57 X 3,389,978 6/1968 Mann et al ..44/57 3,437,465 4/1969 Le Suer 44/57 X 3,501,279 3/1970 Allen et al. ..44/70 FOREIGN PATENTS OR APPLlCATlONS 1,003,746 9/1965 Great Britain ..44/77 Primary Examiner--Daniel E. Wyman Assistant Examiner-W. J. Shine Attorney-.1. Richard Geaman ABSTRACT The invention disclosed herein is a liquid fuel composition having reduced soot and smoking characterized comprising a major proportion of a liquid hydrocarbon fuel and a minor proportion of Group 11A and Group 118 metal salts of carboxylic acids. A preferred fuel composition is from 0.1 to 0.6 percent by weight of bariumand zinc Z-ethylhexanoates admixed in diesel fuel, wherein the weight ratio of barium to zinc is about 10 to 1. Further improvement in smoke and soot reduction is obtained in hydrocarbon fuels when an ether is additionally incorporated into the salt and fuel mixture. A mixture of from about 0.1 to 0.6 percent by weight of barium Z-ethylhexanoate and zinc Z-ethylhexanoate, from between 0.2 to 0.5 percent by weight of the monomethyl ether of ethylene glycol and the balance, a diesel fuel, has substantially reduced smoke and soot forming characteristics.

20 Claims, No Drawings SMOKE SUPPRESSANT COMPOSITIONS FOR PETROLEUM FUELS BACKGROUND OF THE INVENTION This invention relates to new liquid fuel compositions. In particular, it relates to new diesel fuel mixtures with reduced smoke and soot forming properties.

The petroleum industry has encountered serious problems in supplying the demand for middle distillate and heavy residual oils suitable for injecting in to compression ignition engines which will not contribute materially to the pollution of the atmosphere through smoke and soot production. Coupled with this specific need for a diesel fuel mixture with reduced smoking characteristics, there is also an urgent need for liquid hydrocarbon fuel mixtures having improved combustion characteristics for spark ignition and jet engines.

Attempts have been made to reduce the soot formed during the oxidation of liquid hydrocarbon fuels. By way of example, certain metallic smoke suppressant mixtures have been employed in compression ignition engines, but an objection to these mixtures is that they leave deposits in engine crankcases as a result of blowby from cylinders, can be expensive to produce and package, and can form undesirable combustion products in proportion to their content of metal. Further it has been additionally proposed to incorporate various materials into fuels to inhibit their soot, sludge and clogging tendencies. However, some of these materials have proven susceptible to emulsification upon storage and, in certain cases have shown a tendency to lower the Cetane Number of diesel fuels, or reduce the Octane Number of gasoline, while others have reduced the stability of fuel to oxidation during storage.

Accordingly there exists an urgent need to produce a hydrocarbon fuel mixture having reduced smoke and soot forming properties, free of the side effects and deficiencies of the prior art.

SUMMARY OF THE INVENTION It is an object of this invention to provide a liquid hydrocarbon fuel mixture and in particular a diesel fuel mixture, which has reduced smoke and soot forming properties.

It is another object of this invention to provide a fuel mixture having reduced soot and smoke forming characteristics which produces a minimum of ash upon combustion.

It is another object of this invention to provide a fuel mixture having reduced smoke characteristics which has improved oxygen stability as compared to the base fuel.

it is another object of this invention to provide a fuel composition having a Cetane Number and water tolerance characteristics at least equivalent to that of the base fuel, yet which exhibits reduced smoke and soot properties as compared to the base fuel.

It is another object of this invention to provide an improved method for operating an internal combustion engine, and particularly, a compression ignition engine.

Other aspects, objects and advantages of this invention will be evident to those skilled in the art in view of this disclosure.

The objects of this invention are met by dispersing or dissolving in liquid hydrocarbon fuels having a tendency to form soot and smoke on combustion, a minor amount, but sufficient to inhibit said tendencies of Group "A and Group IIB metal salts of organic acids. Mixtures of diesel fuels with barium and zinc salts of alkanoic acids branched in the alpha position have particularly significant reduced smoke and soot forming properties. An especially effective mixture is a mixture of diesel fuel and from about 0.1 to 0.6.percent by weight of bariumand zinc-Z-ethylhexanoates, wherein the weight ratio of barium to zinc metal is about to 1.

Liquid hydrocarbon fuel mixtures having further reduced soot and smoke characteristics are obtained when the aforesaid metal salt-fuel mixtures also have incorporated therein a minor portion of an ether. Glycol ethers and particularly the mono and dialkyl ethers of ethylene glycol, are preferred. Generally, the concentration of ether in salt-fuel mixture should be from about 0.05 to 5 percent by weight. A particularly preferred mixture is a mixture of diesel fuel and from about 0.2 to 0.5 percent by weight of the monomethyl ether of ethylene glycol and from about 0.1 to 0.6 percent by weight of bariumand zinc-2-ethylhexanoates wherein the weight ratio of barium metal to zinc metal is about l0 to 1.

Further, according to the invention there is provided a method for operating an internal combustion engine which comprises passing a liquid hydrocarbon fuel mixture of the invention through the fuel supply system to the combustion chamber of said engine and causing ignition of the fuel therein in normal fashion. This method of operation can be employed in operating a compression ignition engine utilizing the diesel fuel mixture of this invention. In general, the Group "A and Group IIB metals may be combined with any organic acids to form the salts employed in this invention. Such salts can be aliphatic or aromatic carboxylates, e.g., alkyl, aryl, alkaryl, alkenyl, arylalkyl or alicyclic; preferred are aliphatic acids branched in the alpha position and containing up to 30 carbon atoms. Some specific examples of acids are: ethanoic, isopropanoic, butanoic, 2-ethylhexanoic, decanoic, eicosanoic, tricontanoic, benzoic, naphthoic, cyclobutanoic, cyclodecanoic, glycolic, fumaric, and the like. It is to be understood that in each case, the acid anion of Group "A metal salt may be identical to or different from the acid anion of the Group "B metal salt.

Some specific salts which may be combined with liquid hydrocarbon fuels, especially diesel fuel, to form smoke suppressant mixtures include; barium and cadmium Z-ethylhexanoates, strontium decanoate and cadmium 3-methyl nonanoate, barium and cadmium o-propylbenzoates, calcium and cadmium cyclobutanoates, magnesium methylcyclohep tanoate and zinc Z-ethylpentanoate, strontium hexanoate and mercury Z-ethylbutanoate, beryllium and zinc oleates or linoleates, barium fumarate and zinc octacosanoate.

DESCRIPTION OF PREFERRED EMBODIMENTS Enhanced reduction of smoke and soot in fuels is obtained when barium and zinc salts are employed.

Generally it is preferred that the organic acids forming the salts be low-molecular weight aliphatic acids, and especially alkanoic acids having from about four to 12 carbon atoms. The acids are preferably soluble in fuels.

Further improvements in smoke suppression is obtained when the group [IA and group IIB salts of organic acids, especially alkanoic acids having from four to 12 carbon atoms and particularly the barium and zinc salts thereof, are branched in the alpha position.

Examples of suitable salts include those formed by combining any of the group [IA and group IIB metals with any of the acids set forth in the following table:

Group A Group "B Acid Barium Zinc Z-methyl propanoic acid Strontium Cadmium 3-methyl butanoic acid Calcium Mercury Lmethylpentanoic acid Magnesium 2,2-dimcthyl hcxanoic acid Beryllium Z-ethyloctanoic acid 2-propylnonanoic acid Z-methylundecanoic acid 2-2.diethyl hcptanoic acid 2,Zdimethyl decanoic acid Further, it will be recognized that derivatives of the aforementioned metal carboxylates having groups, preferably polar, substituted in place of hydrogen may also be incorporated into hydrocarbon fuels. Such substituents must be essentially nonreactive to the fuel and include, for example, such polar groups as halogen, amino, nitro, nitrate, hydroxyl, and the like.

in another embodiment of the invention, an ether is dissolved or dispersed in the mixtures of group "A and group IIB metal salts of organic acids and liquid hydrocarbon fuels hereinbefore described.

The ethers employed in the present invention are, in general, those having the following structural formula: R(- R-),,OR" wherein n is an integer, preferably between about 0 to 10; R is a hydrocarbyl radical, R" is either hydrogen or hydrocarbyl radical and R is a hydrocarbylene radical, such as methylene, ethylene or the like; and the total number of carbon atoms in a molecule is preferably less than about 30; and

wherein n is an integer preferably having the value of 0, 1 or 2, and R and R' are hydrocarbylene radicals.

Thus,'when R and R" are hydrocarbyl radicals, typical groups include, for instance: alkyl, alkenyl, aryl, alkaryl, arylalkyl, or alicyclic radicals. Examples of suitable hydrocarbyl radicals are: methyl, ethyl, propyl, butyl, isohexyl, 2-ethylhexyl, neodecyl, dodecyl, octadecyl, eicosyl, nonacosyl, phenyl, naphthyl, benzyl, cresyl, ethylphenyl, phenylhexyl, cyclohexyl, cyclopropyl, cyclopentyl, butenyl, octenyl, linoleyl, etc.

When R and R are hydrocarbylene radicals, typical groups include, for example: alkylene, arylene, alkarylene, arylalkylene, alkenylene or alicylene radicals. Suitable hydrocarbylene radicals are: methylene, ethylene, propylene, isohexylene, decylene, phenylene, cyclohexylene, pentenylene, etc.

Examples of simple ethers useful in this invention are: ethyl ether, isopropyl ether, methyl tert-butyl ether, ethyl n-butyl ether, decyl butyl ether, nonacosyl methyl ether, allyl ethyl ether, vinyl isobutyl ether, cyclopropyl methyl ether, cyclobutyl ether, methyl ethyl ether, benzyl methyl ether, benzyl ethyl ether, phcnyl ether, anisole, bis-(Z-chloroisopropyl) ether, and the like.

Examples of hetcrocyclic ethers useful in this invention are: such heterocyclic monoethers as tetrahydrofuran, ethylene oxide, propylene oxide, furan; such heterocyclic diethers as para-dioxane; dioxolane; 2-(3-heptyl) l,3-dioxan-5-ol; 2-(3- heptyl) I,3-dioxolane-4-methanol; and such heterocyclic triethers as sym-trioxane; ethyltrioxane; and the like.

Generally the preferred ethers are those normally liquid mono or di ethers of polyols soluble in fuel. Examples of these ethers are: monomethyl ether of diethylene glycol, monoethyl ether of diethylene glycol, dimethyl ether of propylene glycol, monomethyl ether of triethylene glycol, diethyl ether of dipropylene glycol, and the like. Alkyl ethers of polyoxalkylene glycols having from about three to carbon atoms are particularly preferred.

Especially suitable ethers are the monoalkyl ether of glycols and in particular, of ethylene glycol such as: monoethyl ether of ethylene glycol, monopentyl ether of ethylene glycol, mono(2-ethylbutyl) ether of ethylene glycol, mono(2-ethylhexyl) ether of ethylene glycol, monopentyl ether of ethylene glycol and monopropyl ether of propylene glycol; and the diethers of glycols and, particularly, of ethylene glycol, such as dipropyl ether of ethylene glycol, diethyl ether of ethylene glycol, and dibutyl ether of ethylene glycol.

An other producing unusually good soot and smoke reduction upon addition to diesel fuels is the monomethyl of ether ofethylene glycol. g V

Additionally, fuel mixtures of dialkyl ethers of ethylene glycol, and particularly of dimethyl ether of ethylene glycol,

commonly called glyme, exhibit improved Cetane Numbers, as compared to diesel fuels without said ethers, as well as effective soot and smoke reductions. This improvement is also seen in such dialkyl ethers of polyoxyalkylene glycols as dimethyl ether of diethylene glycol, diethyl ether of diethylene glycol, dimethyl ether of triethylene glycol and dimethyl ether of tetraethylene glycol. Accordingly, sueh ethers comprise anotherpartfularly preferred class of ethers.

it will be recognized that the derivatives of the aforementioned ethers having groups, preferably polar, substituted in place of hydrogen may also be incorporated into fuels. Such substituents must be essentially nonreactive to fuel and include such polar groups as halogen, amino, nitro, nitrate,

.hxdttey apsll s l ke.

Typical fuel mixtures of this embodiment of the invention employable in internal combustion engines include those formed by combining any Group "A salt, any Group "B salt, and any ether, set forth below with a hydrocarbon fuel.

ethylene glycol.

It is recognized, of course, that as the fuel component of the mixture, such hydrocarbon fuels as diesel fuel, gasoline, jet fuels, etc., may be utilized, although diesel fuel is preferred.

Preferred fuel mixtures of this invention containing ethers include:

1. Barium 2-methylpropanoate Zinc 2-methylpropanoate Monomethyl ether of propylene glycol Diesel Fuel 2. Barium Z-ethylbutanoate Zinc Z-ethyloctoate Diethyl ether of pentylene glycol Diesel Fuel 3. Barium 2'methylundecanoate Zinc 2-methylundecanoate Monomethyl ether of triethylene glycol Diesel fuel. Especially suitable fuel mixtures of this invention are: l. Barium 2-ethylhexanoate Zinc 2-ethylhexanoate Monomethyl ether of ethylene glycol Diesel Fuel 2. Barium Z-ethylhexanoate Zinc Z-ethylhexanoate I Dimethyl ether of ethylene glycol Diesel Fuel 3. Barium Z-ethylhexanoate Zinc Z-ethylhexanoate Dimethyl ether of diethylene glycol Diesel Fuel Generally, the mixtures of group "A and group "B salts of this invention may be employed in amounts which produce effective smoke and soot suppression. For this purpose, a minor amount of salts, usually a total of at least 0.05 percent by weight should be employed. Although greater amounts may be employed, generally it is not necessai'y to use more than about 5 percent by weight.

For best results it is preferred that the salts be employed in a total concentration of about from 0.1 to 2 percent by weight.

in the case of the especially preferred diesel fuel mixture of bariumand zinc 2-ethylhexanoates it has been found that best results are obtained when a total of from about 0.1 to 0.6 percent by weight of salts are employed.

Basically the ethers are employed in amounts necessary to produce a significant reduction in the smoke and soot charac teristics of the fuel mixture. For this purpose, generally at least 0.05 percent by weight of ether should be utilized. Although amounts in excess of about percent by weight may be employed, practical smoke and soot reductions are usually achieved with lesser amounts. Best results are attained when the ethers are employed in concentration from about 0.1 to 1 percent by weight.

In the case of the particularly diesel fuel mixtures of bariumand zinc-2-ethylhexanoates and monomethyl ether of ethylene glycol, it has been found that best results are obtained when from about 0.2 to 0.5 percent by weight of ether is employed, and from about 0.1 to 0.6 percent by weight of salts are employed.

The weight percentages of additive are based upon the weight of additive as compared to the total weight of the fuel mixture.

A synergistic effect resulting in improved smoke and soot reduction is observed when the proportion of group IIA metal salts is greater than the proportion of group 118 metal salts. This effect is especially evident where the group [1A salt is barium salt and the group 118 salt is a zinc salt. Further reductions are noticed when the ratio of group [1A metal to group lIB metal, and especially of barium metal to zinc metal in the salts is from about 5:1 to 30:1 and particularly when the ratio is from about 8:1 to 12:1 by weight. For best results it is especially preferred that the weight ratio be about to 1.

An even greater synergistic effect is seen when an ether is incorporated into the aforementioned salt-fuel mixtures. This effect is particularly evident when alkyl glycol ethers, particularly the mono and dialkyl ethers of ethylene glycol, and especially the monomethyl ether of ethylene glycol, are employed.

To enhance the solution of metal salts in hydrocarbon fuels, particularly diesel fuels, it may be necessary to admix the metal salts with an inert petroleum solvent, such as petroleum ether, Varsol, White Oil, the aforementioned ethers, alcohols, especially glycols, and the like and mixtures thereof, in amounts sufficient to form a liquid concentrate with greater solubility in these fuels. On the other hand the salts can be dispersed in the fuel in finely divided form.

To prepare the fuel, salts and ether mixtures advantageously, one may initially dissolve or disperse the metal salts in the ether and then combine said salt-ether concentrate with the liquid hydrocarbon fuel.

In general, any liquid hydrocarbon fuel including heating fuels, and particularly those fuels useful in internal com-.

bustion engines can be employed as the fuel component ofthe compositions of this invention. It is preferred that the liquid hydrocarbon fuel be a diesel fuel having an initial boiling point of 300 F. and an end distillation point of about 750 F. Diesel fuels having a boiling range of from about 400 F. to about 675 F. such as No.2 diesel fuel are especially preferred.

The following examples are given to further illustrate the nature of the invention and are not limitative of scope.

EXAMPLE I In order to evaluate the new smoke suppressant mixtures a 1. Cctane Number, minimum 2. Flashpoint, F. minimum base fuel 3. Distillation recovered, F. maximum 600 4. Viscosity, centistokes at F. 2.14.3 5. Carbon residue (10% bottoms) 0.25

Intake Air Gallery Oil Coolant Firstly, the engine was warmed up on the base fuel at a condition wherein no visible black smoke was observed in the exhaust gases. The fuel flow was increased until the fuel flow was about 13 cubic centimeters per minute corresponding to the appearance of visible black smoke in the exhaust gases and a Hartridge Smoke Number (HSN) reading of about 40.

The smoke suppressant fuel mixture of the invention was then substituted for the base fuel and the engine was run for about 5 minutes to allow stabilization. The smoke meter reading was then recorded. Next a mixture of a base fuel and 0.7 percent by weight of a commercially available smoke suppressant was substituted in place of the additive mixtures as a reference. After 5 minute delay for engine stabilization, Smoke Meter readings were recorded. The cycle of base fuel, additive fuel, and reference fuel was repeated two additional times.

The following table illustrates the effectiveness of the novel diesel fuel mixtures. In the table, the Hartridge Smoke Number (HSN) values are given as the average of the three consecutive runs. The Percent Effectiveness" is represented by the equation [HSN ,,HSN additive] HsN,,,,,-HsN reference] X 109% and is a measure of the efficiency of the novel fuel mixtures, as compared to a commercial smoke suppressant fuel mixture. The weight percent of additive is based on the weight of the metal salts as compared to the total weight of the fuel and salts.

RESULT OF SMOKE SUPPRESSANT TESTS HSN, additive in base fuel Percent effectivenoss Weight HSN, percent of base additive fuel HSN, reference Additive in #1 barium Z-ethylhexanoate, and zinc 2-ethy1hexanoate...-

#2 barium Z-ethylhexanoate and zinc The value of 100 on the Hartridge Smoke Number Scale represents completely black smoke, 30 and below represents a clear exhaust acceptable u nderallrun ning conditions.

The results set forth in the preceding example demonstrate the effectiveness of diesel fuels containing bariumand zinc-2- ethylhexanoates, in reducing smoke and soot formation. The results also demonstrate the synergistic interaction between the barium and zinc salts which is especially evident when the ratio of barium to zinc metal is about 10 to 1. Similar results are obtained when other combinations of group 11A and group IlB metal salts are substituted for the barium and zinc salts in the above example.

Thus when the salts formed by the combination of group 11A metals, group "B metals and the acids listed below are substituted for the barium and zinc-2-ethylhexanoates employed in example i, satisfactory results are obtained.

in order to demonstrate the smoke and soot reduction in mixtures of hydrocarbon fuels, group HA and group 8 metal salts and ethers, a diesel fuel mixture was prepared as follows: about 60 parts by weight of the barium and zinc liquid solution described in example I and containing about 32 percent by weight of barium 2-ethylhexanoate and about 5.4 percent by weight of zinc 2-ethylhexanoate was admixed with about 40 parts of a designated glycol ether. Selected quantities of this concentrate was mixed with the No. 2 diesel fuel described in example i and then introduced into a cetane engine according to the procedure of example i. The reference fuel mixture of example I was also tested in order to provide a standard for comparing smoke and soot reductions. The following table illustrates the effectiveness of this embodiment of the novel diesel fuel mixtures.

RESULT OF SMOKE SUPPRESSANT TESTS HSN, Weight HSN, additive HSN, Percent Additive in percent of base in base referefiecbase fuel additive Iuel fuel ence tiveness Barium 2-sthylhexanoate 0. 13 Zinc 2- hexanoate 0.01 32 5 5 100 Monomethyl ether of ethylene glycol 0.26 #2:

Barium Z-ethylhexanoate 0. 34 Zinc 2-ethylhexanoate 0. 03 38 8 E) 103 Monomethyl ether of Ethylene glycol 0.60 #3 bar um 2-ethylhexanoato 0. 23 55 37 6. 7 38 #4 Zine 2-ethylhoxnnoate O. 39 67 65 i 3 #5 Monomethyl other of ethylene glycol...

it should be noted that the components of the fuel mixtures of this example, when tested individually in diesel fuel showed much less effectiveness in reducing soot and smoke than the combination thereof. This demonstrates that multiple synergism if obtained when the metal salt-fuel mixtures have ethers additionally incorporated.

The results of the preceding example also demonstrate the effectiveness of fuel mixtures of alkyl ethers of ethylene glycol, and especially the monomethyl ether of ethylene glycol and of barium and zinc salts of low-molecular weight alkanoic acids, particularly those acids branched in the alpha position in reducing smoke and soot. Similar results are also obtained when other combinations of ethers and group "A and group "B metal salts of organic acids are substituted for the salts and ethers in the above example. Satisfactory results are obtained when other ethers such as: methyl ethyl ether, dicthyl ether of diethylene glycol, dioxane, and dibenzyl ether are substituted for the monomethyl ether of ethylene glycol.

When other liquid hydrocarbon fuels, such asjet fuel, heating fuel, gasoline, etc., are substituted for the diesel fuel tested, the smoke and soot properties of these fuels are beneficially improved.

,3. EXAMPLE III In order to test the tolerance of the novel fuel additive mixtures of this invention to water, selected quantities of the additives appearing in the table below were dissolved in 100 milliliters of the No. 2 diesel fuel previously described in example i and i0 milliliters of water were added. The diesel fuel mix tures were at room temperature when tested. The water and diesel fuel additive mixtures were shaken vigorously and allowed to settle. The mixtures were observed at periodic intervals for 10 days. The results of the test after 15 minutes are described in the table below.

Water break Weight at oilpercent of water Oil Additives in base fuel additive interface phase No'l'E.-Upon standing for 10 days, no haze was observed in the whiEHHA,

Upon standing for 10 days, no haze was observed in the oil phase.

EXAMPLE IV in order to determine the effect of the new salt-fuel mixtures on the Cetane Number of diesel fuel, a fuel mixture consisting of the No. 2 diesel fuel of example I in admixture with 0.13 percent by weight of barium Z-ethylhexanoate, 0.01 percent by weight of zinc Z-ethylhexanoate, 0.26 percent by weight of the monomethyl ether of ethylene glycol was tested against the No. 2 diesel fuel oil of example i. The Cetane Number of the No. 2 diesel fuel and novel fuel mixtures was determined by operating a single cylinder Cetane Test Engine in accordance with the ASTM procedure D-6l3. The Cetane Number of the No. 2 base diesel fuel was 43.0- -l.0, while the Cetane Number of the aforementioned mixture was 430:1.0.

EXAMPLE V in order to determine the relative stability of fuel mixtures of the invention under aging conditions involving air exposure and in order to evaluate the effectiveness of the additive in inhibiting residue formation and color degradation, the diesel fuel mixture described in the previous example was subjected to the DuPont 300 F. Accelerated Fuel Oil Stability Test.

Fifty ml. of the diesel fuel mixture of example IV was filtered and aged in an oil bath held at 300 F. for minutes. The sample was filtered under vacuum (l6"Hg) through a 4.25 cm. No. l Whatman Paper held in Millipore filter holder. The test tube that held the aged sample was rinsed with 3 ml. portions of n-heptane; each wash being transferred to the filter holder. The filter holder and paper were washed with n-heptane under vacuum until free of fuel oil. The filter was air dried under vacuum and compared with reference standards. A fuel having a matching standard of No. 7 or lower is passing." The No. 2 diesel fuel of example IV was the base fuel. The results of the test showed that the base fuel had a Pad Rating of 7, while the base fuel additive mixture had a rating ff desired, the fuel compositions of this invention may additionally contain oxidation inhibitors, corrosion inhibitors, antifoam agents, other smoke suppressants, sludge inhibitors, color stabilizers and other additional agents adapted to improve the fuels in one or more respects.

it is especially preferred to employ metal sulfonates, particularly the metal alkaryl sulfonates of Group "A metals, especially barium, as an additional additive to the compositions of this invention. A particularly preferred alkaryl sulfonate is barium sulfonate of alkylated aromatics, said barium alkaryl sulfonate having a Molecular Weight of from about 800 to 1,500.

In the fuel additive concentrate of salts, ether and sulfonates added to the fuel, it is preferred that the salts be between about 30 to 50 percent by weight, the ethers be between 25 to 35 percent by weight and the sulfonates be between about 25 to 35 percent by weight, based on the total weight of salts, ether, and sulfonates.

It is particularly preferred that a solubilizer, such as a fuel to be employed, be added to the aforesaid concentrate to form a homogeneous solution and this homogeneous solution be added to the fuel prior to combustion. In this case it is preferred that the salts be between about to 30 percent by weight, the ethers be between about to 40 percent by weight, the sulfonates be between 15 to 25 percent by weight, and the solubilizer be between about 60 to 5 percent by weight, wherein said weight percentages are based upon the total weight of said salts, ether, sulfonate, and solubilizer.

It will be understood that the specific embodiments set forth hercinabove are illustrative only and that the invention is not to be limited except as set forth in the following claims.

Therefore, 1 claim:

1. A fuel composition having reduced smoking characteristics comprising a major proportion of a liquid hydrocarbon fuel and about 0.05 to 5 percent by weight of group [1A and group "B metal salts of alkanoic acids branched in the alpha position.

2. The composition of claim 1 wherein said group A metal is barium and said group "B metal zinc.

3. The composition of claim 2 wherein said acids each have from about 4 to l2 carbon atoms, said liquid hydrocarbon fuel is a diesel fuel and the combined weight percent of barium and zinc salts is between 0.1 and 2 based on the total weight of the diesel fuel mixture.

4. The composition of claim 3 wherein said Group [IA metal salt is barium Z-ethylhexanoate, said Group IlB metal salt is zinc 2-ethylhexanoate, wherein the weight ratio of barium to zinc is about 10 to l, and the weight of said barium and zinc 2- ethylhexanoates is from about 0.1 to 0.6 percent of the total weight of the diesel fuel mixture.

5. A liquid fuel composition having reduced smoking characteristics comprising a major proportion of a liquid hydrocarbon fuel and about 0.05 to 5 percent by weight of group HA and group 1113 metal salts of alkanoic acids branched in the alpha position and about 0.05 to 5 percent by weight of an alkyl ether of a glycol having about 3 to 10 carbon atoms.

6. The composition of claim 5, wherein said fuel is a diesel said glycol ether having from about 3 to 10 carbon atoms, and

said ether is present in amounts from 0.1 to 1 percent by weight based on the total weight o fthe diesel fuel rnix t l. r e.

9. The composition of claim 8 wherein said group [IA metal salt is barium Z-ethylhexanoate, said group "B metal salt is zinc 2-ethylhexanoate, said ether is the monomethyl ether of ethylene glycol, wherein the weight ratio of said barium to said zinc is about 10 to l, and wherein said ether is present in amounts from about 0.2 to 0.5 percent by weight and said metal salts are present in amounts from about 0.1 to 0.6 percent by weight, and said weight percentages are based on the total weight of said diesel fuel mixture.

10. In the method of operating an internal combustion engine wherein a liquid hydrocarbon fuel is passed through a fuel supply system into a combustion chamber of said engine and said fuel is caused to ignite therein, the improvement comprising operating said engine on a hydrocarbon fuel containing about 0.05 to 5 percent by weight of group "A and group 118 metal salts of alkanoic acids branched in the alpha position.

11. ln the method of operating a compression ignition engine wherein a diesel fuel is passed through a fuel supply system into a combustion chamber of said engine and said fuel is caused to ignite therein, the improvement comprising operating said engine on a diesel fuel containing a minor proportion of barium and zinc alkanoates each having from about four to 12 carbon atoms, wherein the combined weight percentage of barium and zinc salts is from about 0.l to 2 based on the total weight of the diesel fuel mixture.

12. The method of claim 11 wherein said fuel mixture is a diesel fuel containing barium 2-ethylhexanoate and zinc 2- ethylhexanoate, wherein the weight ratio of barium to zinc is about 10 to l, and the weight of said barium and zinc 2ethylhexanoate is from about 0.1 to 0.6 percent of the total weight of the diesel fuel mixture.

13. in the method of operating an internal combustion en gine wherein a liquid hydrocarbon fuel is passed through a fuel supply system into a combustion chamber of said engine and said fuel is caused to ignite therein, the improvement comprising operating said engine on a hydrocarbon fuel containing about 0.05 to 5 percent by weight ofGroup HA and Group B metal salts of alkanoic acids branched in the alpha position and about 0.05 to 5 percent by weight of an alkyl ether of a glycol having about three to 10 carbon atoms.

14. In the method of operating a compression ignition engine wherein a diesel fuel is passed through a fuel supply system into a combustion chamber of said engine and said fuel is caused to ignite therein, the improvement comprising operating said engine on a diesel fuel containing barium and zinc alkanoates branched in the alpha position, and an alkyl ether of a glycol having about three to ID carbon atoms, wherein said ether is present in amounts from about 0.05 to 5 percent by weight, said salts are present in amounts from about 0.05 to 5 percent by weight and said weight percentages are based upon the total weight of said fuel mixture.

15. The method of claim 14 wherein said fuel mixture is a diesel fuel containing barium Z-ethylhexanoate, zinc 2-ethylhexanoate, and the monomethyl ether of ethylene glycol, wherein the weight ratio of said barium to said zinc is about 10 to l and wherein said ether is present in amounts from about 0.2 to 0.5 percent by weight and said metal salts are present in amounts of from about 0.1 to 0.6 percent by weight based on t the total weight of said diesel fuel mixture.

16. A smoke suppressant composition suitable for use in liquid hydrocarbon fuels comprising group "A and group "B metal salts of alkanoic acids branched in the alpha position and an alkyl ether of a glycol having about three to 10 carbon atoms, wherein the weight ratio of group "A metal to group llB metal is from about 5 to l to about 30 to l and the weight ratio of said ether to total salts is from about 1 to to about 100 to l.

17. The composition of claim 16 wherein the group "A metal salt is a barium salt and the group B metal salt is a zinc salt.

18. The composition of claim 17 wherein said acids each have from about four to 12 carbon atoms.

from 1 to 3 to 5 to about 1. i

20. The composition of claim 19 wherein l-methoxy-Z- propanol is substituted for the monomethyl ether of ethylene glycol. 

2. The composition of claim 1 wherein said group IIA metal is barium and said group IIB metal zinc.
 3. The composition of claim 2 wherein said acids each have from about 4 to 12 carbon atoms, said liquid hydrocarbon fuel is a diesel fuel and the combined weight percent of barium and zinc salts is between 0.1 and 2 based on the total weight of the diesel fuel mixture.
 4. The composition of claim 3 wherein said Group IIA metal salt is barium 2-ethylhexanoate, said Group IIB metal salt is zinc 2-ethylhexanoate, wherein the weight ratio of barium to zinc is about 10 to 1, and the weight of said barium and zinc 2-ethylhexanoates is from about 0.1 to 0.6 percent of the total weight of the diesel fuel mixture.
 5. A liquid fuel composition having reduced smoking characteristics comprising a major proportion of a liquid hydrocarbon fuel and about 0.05 to 5 percent by weight of group IIA and group IIB metal salts of alkanoic acids branched in the alpha position and about 0.05 to 5 percent by weight of an alkyl ether of a glycol having about 3 to 10 carbon atoms.
 6. The composition of claim 5, wherein said fuel is a diesel fuel.
 7. The composition of claim 6 wherein said group IIA metal acid salt is a barium salt, said Group IIB metal acid salt is a zinc salt, and said salts are present in amounts from about 0.1 to 2 percent by weight based on the total weight of the diesel fuel mixture.
 8. The composition of claim 7 wherein said acids are monocarboxylic acids, each having from about four to 12 carbon atoms and said ether is an alkyl ether of ethylene glycol said glycol ether having from about 3 to 10 carbon atoms, and said ether is present in amounts from 0.1 to 1 percent by weight based on the total weight of the diesel fuel mixture.
 9. The composition of claim 8 wherein said group IIA metal salt is barium 2-ethylhexanoate, said group IIB metal salt is zinc 2-ethylhexanoate, said ether is the monomethyl ether of ethylene glycol, wherein the weight ratio of said barium to said zinc is about 10 to 1, and wherein said ether is present in amounts from about 0.2 to 0.5 percent by weight and said metal salts are present in amounts from about 0.1 to 0.6 percent by weight, and said weight percentages are based on the total weight of said diesel fuel mixture.
 10. In the method of operating an internal combustion engine wherein a liquid hydrocarbon fuel is passed through a fuel supply system into a combustion chamber of said engine and said fuel is caused to ignite therein, the improvement comprising operating said engine on a hydrocarbon fuel containing about 0.05 to 5 percent by weight of group IIA and group IIB metal salts of alkanoic acids branched in the alpha position.
 11. In the method of operating a compression ignition engine wherein a diesel fuel is passed through a fuel supply system into a combustion chamber of said engine and said fuel is caused to ignite therein, the improvement comprising operating said engine on a diesel fuel containing a minor proportion of barium and zinc alkanoates each having from about four to 12 carbon atoms, wherein the combined weight percentage of barium and zinc salts is from about 0.1 to 2 based on the total weight of the diesel fuel mixture.
 12. The method of claim 11 wherein said fuel mixture is a diesel fuel containing barium 2-ethylhexanoate and zinc 2-ethylhexanoate, wherein the weight ratio of barium to zinc is about 10 to 1, and the weight of said barium and zinc 2-ethylhexanoate is from about 0.1 to 0.6 percent of the total weight of the diesel fuel mixture.
 13. In the method of operating an internal combustion engine wherein a liquid hydrocarbon fuel is paSsed through a fuel supply system into a combustion chamber of said engine and said fuel is caused to ignite therein, the improvement comprising operating said engine on a hydrocarbon fuel containing about 0.05 to 5 percent by weight of Group IIA and Group IIB metal salts of alkanoic acids branched in the alpha position and about 0.05 to 5 percent by weight of an alkyl ether of a glycol having about three to 10 carbon atoms.
 14. In the method of operating a compression ignition engine wherein a diesel fuel is passed through a fuel supply system into a combustion chamber of said engine and said fuel is caused to ignite therein, the improvement comprising operating said engine on a diesel fuel containing barium and zinc alkanoates branched in the alpha position, and an alkyl ether of a glycol having about three to 10 carbon atoms, wherein said ether is present in amounts from about 0.05 to 5 percent by weight, said salts are present in amounts from about 0.05 to 5 percent by weight and said weight percentages are based upon the total weight of said fuel mixture.
 15. The method of claim 14 wherein said fuel mixture is a diesel fuel containing barium 2-ethylhexanoate, zinc 2-ethylhexanoate, and the monomethyl ether of ethylene glycol, wherein the weight ratio of said barium to said zinc is about 10 to 1 and wherein said ether is present in amounts from about 0.2 to 0.5 percent by weight and said metal salts are present in amounts of from about 0.1 to 0.6 percent by weight based on the total weight of said diesel fuel mixture.
 16. A smoke suppressant composition suitable for use in liquid hydrocarbon fuels comprising group IIA and group IIB metal salts of alkanoic acids branched in the alpha position and an alkyl ether of a glycol having about three to 10 carbon atoms, wherein the weight ratio of group IIA metal to group IIB metal is from about 5 to 1 to about 30 to 1 and the weight ratio of said ether to total salts is from about 1 to 100 to about 100 to
 1. 17. The composition of claim 16 wherein the group IIA metal salt is a barium salt and the group IIB metal salt is a zinc salt.
 18. The composition of claim 17 wherein said acids each have from about four to 12 carbon atoms.
 19. The composition of claim 18 wherein the group IIA metal salt is barium 2-ethylhexanoate, the group IIB metal salt is zinc 2-ethylhexanoate, the ether is the monomethyl ether of ethylene glycol, the weight ratio of the barium to the zinc is about 10 to 1, and the weight ratio of ether to total salts is from 1 to 3 to 5 to about
 1. 20. The composition of claim 19 wherein 1-methoxy-2-propanol is substituted for the monomethyl ether of ethylene glycol. 